The trend in the circuit protection industry is currently toward complete circuit protection which is accomplished by the addition of supplemental protection apparatus to standard overcurrent protective devices, such as molded case circuit breakers. In the past, when such auxiliary protection apparatus or other circuit breaker accessories were combined with a standard circuit breaker, the accessories were usually custom-installed at the point of manufacture. The combined protective device, when later installed in the field, could not be externally accessed for inspection, replacement or repair without destroying the integrity of the circuit breaker interior. An example of one such factory installed circuit breaker accessory is found in U.S. Pat. No. 4,297,663 entitled "Circuit Breaker Accessories Packaged in a Standardized Molded Case", which Patent is incorporated herein for reference purposes.
A more recent example of a circuit breaker including additional accessories is found in U.S. Pat. No. 4,622,444 entitled "Circuit Breaker Housing and Attachment Box" which allows the accessories to be field-installed within the circuit breaker without interfering with the integrity of the circuit breaker internal components. This is accomplished by mounting the accessories within a recess formed in the circuit breaker enclosure cover.
An electronic trip actuator which is mounted within the circuit breaker enclosure is described within U.S. Pat. No. 4,679,019 entitled "Trip Actuator for Molded Case Circuit Breakers". The circuit breaker trip actuator responds to trip signals generated by an electronic trip unit completely contained within semi-conductor chip such as that described within U.S. Pat. No. 4,589,052. The development of a combined trip actuator for both overcurrent protection as well as accessory function is found within U.S. Pat. No. 4,700,161 entitled "Combined Trip Unit and Accessory Module for Electronic Trip Circuit Breakers". The aforementioned U.S. Patents which represent the advanced state of the art of circuit protection devices are incorporated herein for reference purposes.
An integrated protection unit having both overcurrent protection along with a shunt trip accessory unit is described within concurrently filed U.S. Pat. No. 4,786,885 entitled "Molded Case Circuit Breaker Shunt Trip Unit" and U.S. Pat. No. 4,788,621 entitled "Molded Case Circuit Breaker Multiple Accessory Unit" which Patents are incorporate herein for purposes of reference.
When the integrated protection unit is located remotely from the protected industrial equipment, it is important for the equipment operator to ascertain the status of the operating power supplied to the equipment. An auxiliary switch, installed within the breaker enclosure interacts with the circuit breaker operating mechanism to provide an electronic indication of the "ON-OFF" condition of the circuit breaker contacts, usually by means of color-coded indicating lights. U.S. patent application Ser. No. 229,674 filed Aug. 8, 1988 entitled "Molded Case Circuit Breaker Auxiliary Switch Unit" describes one such auxiliary switch that is field-installable. This Application is incorporated herein for purposes of reference and should be reviewed for its description of the interaction between the auxiliary switch components and the circuit breaker operating mechanism to provide the auxiliary switch function. When such an auxiliary switch is connected by means of external wires, some means are required to prevent damage to the auxiliary switch when undue tension force is applied to the wires. U.S. Pat. No. 4,742,321 entitled "Molded Case Circuit Breaker with Accessory Functions" describes additional wire strain relief devices that are incorporated with the accessory units to protect such units from wire strain damage. This Patent is incorporated herein for reference purposes.
One purpose of the instant invention is to provide an auxiliary switch unit which is field-installable and which is capable of indicating the conditions of the circuit breaker contacts at a location remote from the circuit breaker and is protected from damage due to wire strain without requiring any additional wire strain relief apparatus.